The present invention relates to a power amplifier which amplifies an input signal to a required voltage level.
In communication devices such as a cell phone unit, to reduce areas occupied by built-in components such as a power amplifier and to reduce their costs are critical problems to be solved. For example, Japanese Unexamined Patent Application Publication No. 2005-503679 (Patent Document 1) discloses a distributed power amplifier which efficiently and economically amplifies a radio-frequency signal.
The power amplifier of Patent Document 1 comprises a plurality of push-pull amplifiers interconnected in a circular geometry. An input signal of equal magnitude and opposite phase is inputted to adjacent amplification devices of each of the push-pull amplifiers. A closed loop to which the push-pull amplifiers are coupled functions as a primary winding of a transformer. By further having a secondary winding that matches the geometry of the primary winding, the power amplifier efficiently combines the output power of the individual push-pull amplifiers.    [Patent Document 1] Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-503679